Suillus aestivoluteus R. Zhang, X. F. Shi, G. M. Mueller & P. G. Liu, 2025

Shi, Xiaofei, Zhang, Shiru, Mueller, Gregory M., Liu, Peigui, Yu, Fuqiang & Senanayake, Indunil C., 2025, A subgeneric revision of the genus Suillus (Suillaceae, Boletales) and novel taxa from Eastern Asia based on morphology and multigene phylogenies, IMA Fungus 16, pp. e 144260-e 144260 : e144260-

Suillus aestivoluteus R. Zhang, X. F. Shi, G. M. Mueller & P. G. Liu sp. nov.

Figs 10 , 11

Etymology.

“aestivo-” means summer. This species has very thin and sheer partial veil as a summer version of the European S. luteus , which has thick and wooly partial veils.

Diagnosis.

Morphologically similar to S. luteus but differentiated from it by having thick, persistent and woolly textured annlus or ring, partial veil underneath the ring covers the basal part of the stipe. Glandular dots on lower part of the stipe are covered by the partial veil and could not be seen.

Typification.

China: • Yunnan Province, Lijiang City, Yulong Snow Mountain, Gan Hai Zi (26°46'28.57"N, 100°14'09.55"E, alt. 2611 m), 16 September 2010, Xiaofei Shi, Shi 690 (holotype, HKAS 63212 ) .

Morphology.

Pileus develops from obtuse to convex or flat, 3–12 cm diameter, surface viscid to glutinous, glabrous, background color pallid yellow (4 A 2) to buff brown (5 C 4), with brownish or cinnamon brown (5 C 5, 5 D 5,5E 7) color streaks, not fibrils, underneath the glue. Color streaks are denser and darker in cap center. Pileus cuticle easily separable. Appendiculated with white and membranous partial veils that fall off with age. Hymenophore adnate to subdecurrent, younger ones pallid yellow (3 A 3), turn to dark yellow (4 B 4) with age. Younger ones covered all over by white and membranous partial veils. Do not change color when bruised. Pores 2–3 per mm, small and round. Tubes 3–7 mm deep, concolorous with pore surface. Stipe 2.0–8 × 0.6–2.0 cm, equal to slightly bulbous in base, white or with yellow tinge in apex, solid, glandular dots all over the stipe, color dark brown (5 F 7), become smaller and less towards the base. Annulated with white and membranous ring. Stipe below the annulus covered with sheer remnants of the partial veil, beneath which glandular dots are visible. Annuli turn to buff (5 B 2) or even brownish (5 C 3, 5 D 5), often disappear when old. Mycelia white. Context white to yellowish, 6–15 mm deep in pileus. Stipe context concolorous. Do not change color when exposed. Spore print cinnamon brown (5 E 7, 5 F 7). Odor and taste indistinct.

Basidiospores [80 / 2 / 2] 7.0–9.0 (9.5) × 3.0–3.5 (4) μm, Q = (2.00) 2.14–2.71 (2.83), Q sd = 2.43 ± 0.21, smooth, oblong in face view, narrowly inequilateral with a hilar appendage in profile view, hyaline yellow or brown in KOH, tawny yellow in Melzer’s. Basidia 4 - spored, clavate, bulbous top, 20.0–22.0 × 5.5–7.0 μm, hyaline yellow or brown in KOH, tawny yellow in Melzer’s. Hymenophoral trama divergent, wrinkled, thin-walled, hyaline and mostly 5–10 μm, up to 15 μm. Pleuro- and Cheilocystidia in fascicles, abundant, clavate, content brown or hyaline, surrounded by brown amorphous materials in KOH, up to 70 μm long. Caulocystidia abundant in all part of the stipe, morphologically similar with pleuro- and cheilocystidia, encrusted with too much brown pigments, up to 100 μm long. Pileipellis an ixocutis, hyphae hyaline, thin-walled and encrusted with ochraceous granules, scattered in glue, most 3–7 μm, up to 13 μm wide. Stipitipellis mostly composed of interwoven hyphae, covered by brown amorphogous pigments, about 3–9 μm wide. Context trama hyaline, smooth, thin-walled, interwoven, similar for pileus and stipe, mostly 3–30 μm, up to 50 μm wide at stipe base. Clamp connections absent.

Habitat.

Usually gregarious, in association with Pinus yunnanensis .

Known distribution.

Currently only known from southwestern China within the range of Pinus yunnanensis .

Specimens examined.

China: • Yunnan Province, Diqing Tibetan Autonomous Prefecture, Shangri-la Town, Xin Sheng Qiao forest park (alt. 3317 m), 17 September 2010, Xiaofei Shi, Shi 699 ( HKAS 63204 ) ; China: • Yunnan Province, Heqing Xian, Song Gui Town (alt. 1600 m), 10 October 2011, Xiaofei Shi, Shi 1018 ( HKAS 71991 ) ; China: • Yunnan Province, Weixi Town, Tacheng Xiang, Bazhu village (alt. 1900 m), 15 October 2011, Xiaofei Shi, Shi 1032 ( HKAS 72004 ) ; China: • Sichuan Province, Xicang City, Puge Town, Luoji Mountain, outside Xianren cave (alt. 2000 m), 12 September 2010, Xiaofei Shi, Shi 673 ( HKAS 63183 ) .

GenBank.

ITS = KU 721214 ; LSU = KU 721393 ; TEFα- 1 = KU 721602 ; RPB 1 = KU 852247 ; RPB 2 = KU 852310 .

Notes.

Sister to this new species, Suillus luteus grows in Europe with Pinus sylvestris and has been introduced to North America along with the host tree. Suillus luteus collections from northeastern China associate with P. sylvestris var. sylvestriformis and it is the same European Suillus luteus species.

Figures

Figure 10. Basidiomata of Suillus aestivoluteus (holotype, HKAS 63212). Scale bar: 5 cm.

Figure 11. Suillus aestivoluteus (holotype, HKAS 63212). a Basidiospores; b Cheilocystidia; c Hymenium with basidia; d Pileipellis (mature specimens). Scale bars: 5 μm (a); 20 μm (b – d).